by Roy W. Spencer, Ph. D.
This is an update to my previous posts [here and here on WUWT] describing a new technique for estimating the average amount of urban heat island (UHI) warming accompanying an increase in population density. The analysis is based upon 4x per day temperature observations in the NOAA International Surface Hourly (ISH) dataset, and on 1 km population density data for the year 2000.
I’m providing a couple of charts with new results, below. The first chart shows the global yearly average warming-vs-population density increase from each year from 2000 to 2009. They all show clear evidence of UHI warming, even for small population density increases at very low population density. A population density of only 100 persons per sq. km exhibits average warming of about 0.8 deg. C compared to a nearby unpopulated temperature monitoring location.
In this analysis, the number of independent temperature monitoring stations having at least 1 neighboring station with a lower population density within 150 km of it, increased from 2,183 in 2000, to 4,290 in 2009…an increase by a factor of 2 in ten years. The number of all resulting station pairs increased from 9,832 in 2000 to 30,761 in 2009, an increase of 3X.
The next chart shows how the results for the U.S. differ from non-US stations. In order to beat down the noise for the US-only results, I included all ten years (2000 thru 2009) in the analysis. The US results are obviously different from the non-US stations, with much less warming with an increase in population density, and even evidence of an actual slight cooling for the lowest population categories.
The cooling signal appeared in 5 of the 10 years, not all of them, a fact I am mentioning just in case someone asks whether it existed in all 10 years. I don’t know the reason for this, but I suspect that a little thought from Anthony Watts, Joe D’Aleo & others will help figure it out.
John Christy has agreed to co-author a paper on this new technique, since he has some experience publishing in this area of research (UHI & land use change effects on thermometer data) than me. We have not yet decided what journal to submit to.
I’ve identified a new phenomenon which I am dubbing the CRU Heat Averaging Effect.
Examination of the latest Hemispheric and Global Averages Graph (http://www.cru.uea.ac.uk/cru/data/temperature/nhshgl.pdf) posted by the Climate Research Unit reveals the following:
The statistical trend line for northern hemispheric temperatures peaks in 2003.
The statistical trend line for southern hemispheric temperatures peaks in 2004.
The statistical trend line for global temperatures peaks in 2005.
Interesting math.
OK. Looked at the “raw” numbers and that’s what comes out of the five year trend line.
NickB. (07:17:20)
Pascvaks (05:20:42)
Hey, taking your comments upside-down is great way to prove CO2 has no local heat effects at all. Thanks for the reverse tip!
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George E. Smith (18:18:04) :
My Physics Handbook gives the Total Kinetic Energy for an (ideal) gas as being (3/2)N.k.T where N is the number of particles, or the mean Kinetic energy per particle as (3/2)kT, which would then seem to apply also to a non-ideal gas since it is a per particle (molecule) energy. k is of course Boltzmann’s constant.
<<
I learned that it was (1/2)*k*T for each degree of freedom. For a monatomic gas, (3/2)*k*T is correct. For a diatomic gas, it becomes more complicated. I’ve seen (3/2)*k*T, (5/2)*k*T, and (7/2)*k*T depending on the temperature. At room temperature, then (5/2)*k*T works for a diatomic gas. You’ll notice that most of the atmosphere is composed of oxygen and nitrogen and those gases are usually diatomic. When you add in carbon dioxide, methane, water vapor, ozone, various noble gases, and other trace molecular gases, then the actual formula is not that simple.
Jim
Merrick (07:22:42) :
Whatever happened to the warm period in the 1930s, it isn’t in either the NH or SH?
“”” Jim Masterson (08:15:55) :
>>
George E. Smith (18:18:04) :
My Physics Handbook gives the Total Kinetic Energy for an (ideal) gas as being (3/2)N.k.T “””
Well I learned about the same Jim, which is why I wrote:- “for an (ideal) gas”
Phil and I have had this discussion before.
Of Course, the concept of an ideal gas, containing N point like particles, can only have the three translational degrees of freedom, and its rotational energy would have to be zero since such particles would have no moment of inertia.
The (5/2).kT for a diatomic gas assumes a dumbell molecule, which would add two rotational degrees of freedoma perpendicular to the axis of the molecule. The moment of inertia for rotation about the molecule axis is assumed zero, but I suppose in reality it isn’t quite zero. The nuclear component must be PDsmall, but the electron clouds probably have some moment of inertia more than zero.
But for any gas (atmospheric) mixture each component still has a total energy that is linear with T, so the mixture would also seem to be linear with T.
My Quantum mechanics is only of restricted extent, so I’m not up on the possible couplings between various modes in a polyatomic molecule; I’m guessing that Phil knows all of that stuff.
In any case, I believe that the thermodynamic Temperature scale is only defined in terms of an ideal gas, so the scale itself is quite linear. The question becomes one of how linear with the real thermodynamic Temperature scale, is the atmosphere’s total energy. Maybe ?
What do you think ?
Is there no sattelite that has some version of a FLIR camera that can just look down at cities and measure the UHI directly? Seems like something that could be done relatively cheaply with weather balloon and a camera and an enterprising grad student.
Back to the central subject of this thread, which is this interesting evidence that Dr Spencer and Prof Christy are working on showing an effect of “civilization” on local heating, or UHIs if you will.
It seems irrefutable that any changes in the natural planet as Gaia made it, would change the thermal processes. Hey wait till you see what going solar is going to do to the thermal processes (in theory).
I see the problem, not as a problem that human contraptions get hotter than Gaia’s contraptions; but when it comes to counting up those effects, we aren’t doing that properly.
The elevated temperature of a UHI is not of itself a problem. The problem arises, when we take the temperature on the runway at San Jose (International) airport, and try to claim that that is what I must be enjoying, when I am out fishing in the middle of the sea of Cortez 1200 km away.
We have to stop extending the influence of UHIs beyond where Gaia says they are getting in her hair.
toyotawhizguy (18:50:14) :
If you want to estimate anthropogenic joule heating of the globe, you need to take the ratio of total anthropogenic joules to incoming sun joules (insolation) for the same time period.
Except you leave out latent Geologic heat from Earth’s core, and it surface radiation via volcanic activity. The correct approach would be to add Gj to insolation Ij.
The smaller US UHI-related warming agrees with McKitrick and Michaels finding of generally smaller warming bias in the US vs the rest-of-world. Then when one considers all of the US measurement station problems unearthed by Anthony’s army of volunteers, one realizes how shoddy the data from the rest-of-world actually is.
Chris (10:37:37)
I’ve had the same thought. I also had the silly thought of using near surface (but sub surface) temperature readings as a natural way of averaging out surface temps. I read somewhere that, I think, 6ft below the ground (at least in zones that are not geotherm active) the temperature will be the average of the surface temp.
Another approach, which might be more effective for researching the UHI effect on surface temperature records, would be to surround a structure (maybe an asphalt parking lot, power sub-station, house, etc) with an array of thermometers 2m off the ground (i.e. replicating a the temperature stations) so the effect can be demonstrated spatially. A similar exercise could be performed around a city.
Anyway, sorry to be OT again ; )
Actually, the rotational moments of inertia for atomic species and about the axis of linear molecules is VERY large, as opposed to either zero or very small (it’s a lever-arm argument and the lever arm is essentially zero). The kinetic energy of a “thermalized” molecule is the sum of 1/2 k T for each accessible degree of freedom at temperature T. The translational degrees of freedom have, as far as we can tell, continuously graded energy levels (i.e., they are classical degrees of freedom and not quantized). For non-atomic species the rotations are quantized, but for many or most species the energy spacing is very low. Because of this many rotational states (l=0,1,2,…) are at or below the available free energy (k T) so that the rotational state populations are typically populated in a pseudo-classical (the state populations are Gaussian-like) manner. For each quadratic mode of a species that can be said to populated in this classical manner there is a contribution to the overall kinetic energy of 1/2 k T, as stated before.
For monoatomic gases, therefore, the kinetic energy is 3/2 k T since there are only 3 translational degrees of freedom and no *accessible* rotational degrees of freedom (all species are in the ground rotational state – the first excited rotational state of atomic species is typically an x-ray or gamma-ray transition and is in fact an energy transition of the nucleus – and therefore not accessible *thermally* at atmospheric temperatures).
For diatomic gases there are two typically accessible rotational degrees of freedom (the axial rotation is again an x-ray transition) and can contribute therefore as much as 2 * 1/2 k T to the kinetic energy, or 5/2 k T. Here come the next two big caveats. One – those accessible degrees of freedom, as mentioned before, have to have inter-state energy spacings much smaller than the thermal energy or they will NOT be populated in a near-classical (Gaussian-like) way. Like the high-energy axial-rotation case they will have all or almost all of their state population in the ground state or the ground state and the first excited state. It depends on the moment of intertia. Diatomic molecules with very *high* moments of intertia (like iodine or bromine) have very *small* energy spacings bettween rotational states. They are, therefore, usually considered “classical” rotors ate low temperatures and have very classical-like state populations and threfore also have total kinetic energies very close to 5/2 k T (wait, there’s another consideration). Light molecules, like H2, have very LARGE energetic spacings between rotational states (on the order of 0.1 eV, and kT at room temperature is about 0.025 eV) so that almost all of the rotational state density of H2 is in the ground rotational state for H2 at room temperature. So the total kinetic energy of H2 is pretty close to 3/2 kT (at room temperature) even thought it’s a diatomic molecule. So, obviously, at high temperatures all diatomic molecules can have a kinetic energy near 5/2 k T and at low temperatures nearly all diatomic molecules can have a kinetic energy near 3/2 k T. One often speaks of the “characteristic rotational temperature” of a molecule. This temperature is the temperature at which k T is approximately equal to the rotational state spacing of the molecule and therefore the temperature at which rotational degrees of freedom start to affect the total kinetic energy.
The next major caveat is vibrations. All of the same arguments apply and there is also a “characteristic vibrational temperature” that works exactly the same way it did for rotations. A molecule like H2 has a very high characteristic vibrational temperature so its vibrational degree of freedom at room temperature is dominated by the ground state and it makes virtually no contribution to the total kinetic energy. The same can be said for most atmospheric constituents. A diatomic molecule like iodine or bromine would, however, have a significant contribution from the vibrational degree of freedom at toom temperature and therefore have a total kinetic energy between 5/2 k T and 3 k T.
It get’s more complicated for polyatomic species.
Too long, not gonna edit for content. Sorry for any typos, etc.
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David Schnare (16:39:52) :
Roy:
Until you can convince me that the stations themselves are not corrupt for micro-climate influences, your entire approach is as suspect as Jim Hansen’s luminosity approach. I simply don’t see the physics of a massive jump in UHI for population densities below 100 persons per sq. km. Unless you address how much energy has to be generated by the 100 persons to generate a heat capacity that releases in a manner that raises the mean temperature, you are just playing with the numbers.
*******
If you look at the numbers that have appeared on this site before, you’ll know that as far as the UHI effect is concerned, energy usage is actually small compared landscape changes (perhaps Barrow, AK & other Arctic sites would be an exception). Brick walls, asphalt roads, clearing of vegetation all have much larger effects due to changes in solar absorption, heat-retention, water-evaporation or wind-blockage than energy-usage does.
I feel sorry for Dr. Spencer as so many of the comments appear to be off base. Certainly it is interesting to study many different UHI impacts, like brick building vs. steel, airport changes, gdp, elevation, societal differences, windy vs. windless conditions, and so on, but none of it matters to Dr. Spencer’s analysis!
His analysis is all of these things averaged together. One could look at many other factors and possibly determine some interesting things, but if you want to develop a correction for UHI effects to apply to the global temperature record for determining global temperature trends, there is no need! Certainly some growing population centers, if analyzed individually, will exhibit a greater UHI than Dr. Spencer’s method; some will show less. It doesn’t matter. It also doesn’t matter why there are differences. The global temperature trend is a giant average. The only thing you need to correct the trend for UHI is an ‘average’ correction. The individual station histories (the physical changes around them) are not relevant if you do it this way. (Relocations and changing thermometers would still be relevant and need of additional corrections.)
Simply look at the population change around each location from the beginning of the record to the end and apply the appropriate corrections along the way, then add the corrected data to the file that goes into determining the global trend. That is what they have been doing all along to ‘correct’ for UHI, the only difference is that they used the Jones et el method from around 1990, that Jones now openly admits was wrong. (Many people knew this from the beginning, but couldn’t prove it because it was based largely on bad data from China that no one had the means to dispute.) Dr. Spencer’s method is much, much better, for it is based on all the available data, not just a few choice locations.
Aside from the global temperature trend, there is really not much reason to be concerned with UHI at all, so determining the specific UHI for each location is a lot of work for little purpose, when the average UHI effect is all that is really needed to determine the average global temperature trend.
“”” Merrick (08:04:05) :
Actually, the rotational moments of inertia for atomic species and about the axis of linear molecules is VERY large, as opposed to either zero or very small (it’s a lever-arm argument and the lever arm is essentially zero). “””
Yikes !! I do love it when my “stick in the sand” scratchings, stimulate the noggins of others who know the real scoop.
So thank you Merrick for your long post, typos and all, if any; it is safely stored now as a WORD file in my Climate folder.
But now you need to explain some things which I seem to be stuck on; specifically that first sentence above.
Thinking in terms of a stone age “planetary” model of an atom, I assumed that the nuclear mass was so tiny, radius wise, that its moment of inertia would be very small in the molecular scale of things, so the atom moment of inertia would be just due to the much lighter elctrons but now at some sizeable radius (so I AM puzzled when you say the lever arm is essentially zero). Now I can see, that even in such a bricks and mortar model, those things do have dimensions that aren’t zero, so the moments too wouldn’t be, and I guess if you spin fast enough you can get some real angular momentum going. But does say, an Argon atom have a moment of inertia anywhere comparable to say a CO2 rotating about the C; perpendicular to the molecule axis ?
And then for the dumbell diatomics like O2 and N2, what is the rough relative sizes of the moments spinning on the molecule axis, versus perpendicular to that axis. The (5/2)kT form presumes that it is negligible in comparison.
But then, I suppose, even given a small moment, one could still store energy; you just have to spin a damn side faster. Then I suppose there is the whole issue of just how do you couple energy into those modes.
The “ideal” gas concept assumes point like particles so it essentially defines rotational moments as non existent; hence the (3/2)kT.
But back to your dissertation above. Can you recommend any standard textbook that teaches that stuff at about that level. I think I can get my teeth around things at that level; with the right text book. I gave up on Reviews of Modern Physics years ago, when I found whole papers where I couldn’t even understand any word with more than four letters.
For the last umpteen years, I have been buried in the Solid state Physics of semiconductors, to the point where I have forgotten most of what little I used to know about atomic/molecular spectra in gases.
So if you know what the OED of atomic/molecular physics is at that level, It would be very nice to get.
But I’m still puzzled by the notion that the moment is large because the lever arm is small, as you put it above ?
I almost added this to my post above, but it deserves a separate response. There is only one time that my jaw dropped while reading all of the above comments, and that was the comment at (16:39:52) from this man:
David Schnare, Ph.D.
Center for Environmental Stewardship
Thomas Jefferson Institute for Public Policy
He wrote:
“Unless you address how much energy has to be generated by the 100 persons to generate a heat capacity that releases in a manner that raises the mean temperature, you are just playing with the numbers.”
A few, like beng, have addressed this comment very nicely. I will not be so nice.
I am absolutely appalled that someone with a Phd, working for an environmental group for the purpose of influencing public policy, would believe that UHI’s are the sole product of how much heat people release into the atmosphere! Maybe he has a Phd in social studies or economics or something, but it better not be in a physical science. If it is, than he must have purchased one from a university, because he certainly didn’t earn it.
The fact is that you can have a UHI develop if there is only one person in that square kilometer for the entire length of the temperature record, never releasing any heat other than from his body. If that one person turns an open field into an expanded driveway, builds a tennis court and a large home (that he never heats internally, just for the sake of argument), near the observation site, there will be a significant UHI effect. Sure, if you are constantly pumping the exhaust from a heat source directly at your thermometer, than the heat generated by humans will make a difference at that particular site, but the vast majority of sites do not have that, and the indirect heat humans produce, bleeding into the atmosphere from homes, buildings, cars and so on, is usually negligible compared to the impacts of solar energy on varying surfaces.
If Dr. Schnare is an example of the level of ignorance that goes into the generation of public policy, then we need not fear global warming or nuclear war. We will all be dead of stupidity before anything else!
Hi George,
Sorry, mistyped and didn’t edit! It’s a question of energy, not momentum, per se, and their relationship.
The rotational energy is:
E = L(L+1)/(2 I), where L is the rotational quantum number, I is the rotational moment and I = m R^2 and m is the reduced mass of the system
If, as in the case of axial rotation of a diatomic molecule (or rotation in any axis for an atom) the lever arm length, R, is nearly zero (momentum is very small), you can see that to transition from the ground rotational state (L = 0; E = 0) to the first excited state (L =1) or higher will take a LOT of energy.
Let’s look at some real numbers…
The internuclear distance for ground state H2 is about 740 pm and the diameter of the hydrogen nucleus is on the order of about a femtometer. So the transition 1 <- 0 for the axial rotation is about (740/0.1)^2 times as energetic as the 1 <- 0 transition for one of the two perpendicular rotations. That's a hard gamma ray. That's the extreme example. In most cases the nuclear diameter is about an order of magnitude larger than that, so that the transition ratio is about 100 times less.
So, as you say, the moments are very small along the internuclear axis – this means the transition energies are very large.
As you say, the contributions of the axial rotational degree of freedom for diatoms is VERY small. These perpedicular for "heavy" molecules like O2 and N2 make those rotations very "classical" at room temperatures. So 5/2 k T is expected for them. Very light diatoms like H2 have kinetic energies at room temperature much less than 5/2 k T. And again for the same reason. For the very light molecules even the moments perpendicular to the internuclear axis are relatively small (compared to k T) so that even those degrees of freedom end up contributing much less than 1/2 k T each to the total kinetic energy.
Sorry for the confusion on my mistatement regarding momentum.
OED? Oxford English Dictionary?
Make that (740/0.001)^2 – I hate re-reading what I type!
All attempts to systematically quantify UHI effects either individually or in some aggregate average sense should be welcomed. With almost all long-term temperature records coming from population centers, rather than from pristine green fields, intensification of urban heating by a variety of factors is what introduces positively trending bias in most records. Yet, the wide range of results shown for different years here suggests that that something besides the population density per se affects the temperature elevation in population centers. Much as I would welcome a reliable UHI “correction” for the bias in the aggregate “global” record, we’re still far from a solid basis for making such corrections. Perhaps the best that can be done is to exclude the patently corrupted records and compile estimates from from far fewer, less-biased records.
“”” Merrick (10:48:21) :
Hi George,
Sorry, mistyped and didn’t edit! It’s a question of energy, not momentum, per se, and their relationship. “””
Well my mind was sort of fixated on Infra-Red molecular situations. Funny thing is at one time or another I have worked in some way, all the way from down to (but not including ) DC out to Cosmetic Rays; perhaps with the exception of X-rays, although I did once work on an exploding wire contraption up in McMinville Oregon once; which made hard X-rays for x-raying steel or cast iron to look for flaws; but I only worked on the fast pulse generation that was going to blow the tungsten wire to smithereens.
But you’re talking to a chump who lost all his High School, and University text books; actually about 49 years ago tomorrow, as it turns out; so the noggin is slowly losing what was once in there.
So if you can refer me to a modern college text, at Masters/PhD level, it would certainly help stem the outflow.
And yes you pegged the OED part.
Thanks
There was a time, when I thought that spectroscopy was just the neatest thing since sliced bread. In my Freshman Physics year, we had to do a two day lab using a 1 cm Fabry Perot Etalon, along with a dispersing prism, to measure the wavelength of some red line, in the spectrum of Neon; they claimed you could measure a couple of lines to better than 0.01%.
I started digging into the theory of the Fabry Perot Interferometer, and about a month later, I presented the Prof with a list of about 22 red (mostly) Neon lines each, called out to 8 significant figures. It seems that somewhere in there I had to use a Mercury 198 source lamp as my primary reference.
You probably won’t believe this but I actually use the wavelength of a spectrum line, along with some other descriptors to come up with a 12 character password, that somehow I have remembered for about 50 years; but it isn’t one of those Neon lines. And I can use the same password with some character transpositions for my ATM PIN number, now that my bank can take from 4 to 12 digits.
PS. the main reason I avoided the DC case was so I could turn the power switch on. (and off)
Jim Clarke,
There is a big difference between doesn’t matter and doesn’t matter to Dr. Spencer’s analysis. I agree, and have even said as much in my posts, that microclimate analyses are OT for his work, but at the same time it is an area that has not been adequately studied – especially as it pertains to potential skewing of temperature records. What happens when an asphalt road is laid 10ft away from a station, 100 ft, etc – nobody knows. Many (most?) here suspect upward bias in general, many suspect bias effect in particular on Tmin, and consensus theory claims anywhere from no effect to they’ve already corrected for it.
I look at it this way, Dr. Spencer is coming at it from a macro perspective – it’s great work and needs to be done. Some here, like me, are more interested in looking at it from the micro perspective. That’s not to say Dr. Spencer is wrong – far from it – we’re just looking at it from the other direction.
That said, he’s already identified at least one significant difference between the US and the rest of the world, and on his first post many posited that these trends would vary on a country and/or latitude basis. There were also questions – on his second post I believe, the snapshot of 2000 – about how consistent the relationship would be year over year, which this analysis seems to show unexplained variation – which could just be noise, or could be a sign of something else all together. I’d tend to say the one thing left (assuming US vs. rest of the world is the only significant variation in the shape of the relationship and not latitude or other country/regional differences) would be to run the analysis here for the full range (1990-current) to see if the variation is relatively constant or varies over time. It probably wouldn’t fit, but I would also be very curious about seasonal impact/differences from UHI as well.
So how irrelevant is our bantering about land use, developmental and consumption differences between countries, regions or latitudes? Maybe not as much as you think…
NickB,
I am sorry if I misunderstood the discussion of microclimates. I was taking those comments in this thread as ‘shortcomings’ of Dr. Spencer’s argument, as if he needed to consider these things for his method.
I think we really agree on everything. I didn’t mean that the study of microclimates is irrelevant, only that it is not necessary to consider the microclimates to develop a workable UHI correction for the global temperature trend.
Could the cooling effect in the US at low densities be forest clearance-wind effects? Someone mentioned the gold course effect, but greening would lower albedo-and increase temps? Wouldnt-it? This study should be followed up by using station pairs classified by land use ie. % rock-bare soil/farmed land/forest/urban…
Kudos to Dr. Spencer for his investigations into the UHI topic. Although his initial interest may have been limited and observational, it (obviously from the comments) unearths a bevy of questions about causation. He may have hit the jackpot on unanswered questions.
If you model the power dissipation of a human, and the power he uses, you will see that by the time he reaches the population density of Manhattan, man is (in the aggregate) swamping insolation even during the day. Smaller cities get there at night, affirming the many comments that the UHI effect is strongest then. Lower concentrations yet cannot be so directly driven, but depend on land use changes. The stunning difference between the consequences of those changes in the US and non-US seems likely to result from their different tactics.
I hope that we will see this area studied in detail in the coming years.
Jim Clarke,
No worries good sir!
If there is/was any indication here that because Dr. Spencer was not approaching this from a micro standpoint his work is somehow invalid, then I take no exception to your comments whatsoever. I hope I never gave that impression with what I wrote, and if I did (or anyone else did) a correction was most definitely in order.
At some point (I think regional and latitude analyses), pushing his approach too far down to the micro scale would result in an attempt of “boiling the ocean”… so you have to draw the line somewhere.
———————–
Now at the risk of going OT again, I do think there is a (possibly rhetorical) question of paradigm that is worthy of discussion at some point, and that is… should we really be correcting UHI out of the temperature records or should we be measuring it? I think this goes hand in hand with the more pressing question of what is an appropriate minimum resolution for the surface temperature record (ex: I believe GISS extrapolates up to 1200km in the Arctic)? Today, GISS claims UHI is possibly overcorrected out of their reconstruction (although at the same time they have the hottest map around). I believe CRU does little to no correction, and I’m not quite sure what the two other surface sets do. More than likely, IMO, this results in what sould be small(ish) red dots of UHI instead being big(ger) orange blobs of “climate change” in the surface records. From a lower troposphere (sat record) viewpoint, because of convection and wind… I’d posit that UHI would also show up as blobs there. What this means is that any error in UHI correction, in either direction, would result in a diffused effect in the grid (if not surrounding grids) just the same way that UHI affects it.
On the long term I think that getting a more micro understanding of the spatial effects of urban development (both how it affects surface stations and sat readings) will be crucial to our understanding and analysis of the surface temperature records. Doing so would probably also require information at a resolution that is not available today
For now, with the information available, I’m not sure if there is any better approach one could take than Dr. Spencer’s work here.